Re: [ATM] BVC material properties

[George Anderson <tillerman1@videotron.ca>]

Hi James

Secret isn't the right word now that I think about it, I am trying to 
think of how Andre referred to the glass but I can't come up with the 
right word.
Due to its low expansion I have always (quite possibly wrong) thought 
that he may have been using the ceramic glass that is used in the doors 
of woodburing stoves. I know that mine can handle a temperature 
differential that is quite impressive, and it allows the heat to pass 
though quite well.
I'll have to do a search on the archives for Andre's posts to see just 
what the word was that he used. Hopefully it wasn't in an e-mail 
directly to to me as my harddrive has changed a few times since 
2001-2002 when he was on the list.

George Anderson
Montreal Canada

Clear skies and good health

James Crombie wrote:
> George
>  I didn't think there was any secret to the glass, it was more in the 
> heating and cooling process that turned it into the vitified ceramic.  
> He probably starts with a plain window glass (my guess)  I wonder if he 
> had been aiming for it or if it was a lucky accident  that he managed to 
> be able to reproduce.
> 
> James Crombie
> http://www.jamescrombie.com
> 
> George Anderson wrote:
> 
>> Mark Holm wrote:
>>  
>>
>>> Tom Krajci wrote:
>>>   
>>>>> From: George Anderson <tillerman1@videotron.ca>
>>>>>       
>>>>> The mirror blanks are made from layers of BVC that are fused together.
>>>>>       
>>> According to Andre, also on this list several years ago (as I recall),
>>> the glass does not come from Pilkington in the BVC form.  He does indeed
>>> fuse stacks of sheets together.  In the fusing process, he also uses the
>>> heat to modify the glass micro structure, producing the BVC product from
>>> a starting material that was glassy and (probably) transparent.  At
>>> least one list member has attributed this transformation to
>>> "devitrification", a phenomenon in which prolonged heating at the right
>>> temperature causes crystals to precipitate in some glass compositions.
>>>
>>>   
>>
>> Hi Mark
>>
>> I remember Andre on the list having to defend his product. At one 
>> point he was referring to a "secret glass" from Pilkington. I guess 
>> that changed.
>> Interesting the theory about the devitrification, since the official 
>> name for BVC is "Black Vitrified Ceramic".
>>
>> George Anderson
>> Montreal Canada
>>
>> Clear skies and good health
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>>
>>
>>  
>>
> 

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